JP2000181321A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent image flow even when the moisture content of the peripheral environment changes by operating an electrostatic charging means, exposing means and cleaning means right after the image area after a specific number of times of image formation is counted when the moisture content of the peripheral environment is judged to be above the specific moisture content. SOLUTION: When the environment is detected to be the moisture content W>=9 g as the specific moisture content region, the high-moisture environment is judged. The 200-th sheet when the specific number of sheets (interval specific number of sheets) default of the integration counter of copying and printing is defined as 200 sheets is decided as a copying start. Operation is so carried out that post-rotation black charge is carried out after post rotation at the time of ending of a job by detecting the attainment of the specific number of sheets. A drum drive motor is kept operated and idling of the drum is executed even after end of the laser exposure of the image region. Simultaneously, an image receiving device drive motor is operated and the sleeve rotation of the developing device is executed. Further, simultaneously, a cleaner system drive motor (main motor) is driven and the idling of the cleaner system is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine and a printer.

[0002]

2. Description of the Related Art In recent years, an image forming apparatus has been actively proposed as a digital data information transmission by a data communication network and a hardware output device of the information. As this type of image forming apparatus, there is a digital printer or a digital copying machine.

FIG. 19 shows a schematic configuration of a digital printer. The photoconductor (photosensitive drum) 1 is provided with a photoconductive layer on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. Around the photosensitive drum 1, a scoro-to-cone charger (primary charger) that uniformly charges the surface of the photosensitive drum 1 substantially in the rotation direction.
2. An original is read, the photosensitive drum 1 is exposed based on an image signal proportional to the density of the image, an exposure device 3 for forming an electrostatic latent image, toner is attached to the electrostatic latent image and developed as a toner image The developing device 7, a corona transfer charger (transfer charger) 8 for transferring the toner image formed on the photosensitive drum 1 onto a transfer paper P as a transfer material, and the transfer paper P on which the toner image has been transferred to the photosensitive drum 1. An electrostatic separation charger (separation charger) 9 for separating the toner image, a cleaning device 13 for removing the residual toner on the photosensitive drum 1 after transferring the toner image, a pre-exposure lamp 30 for removing the residual charge of the photosensitive drum 1, and the like. Is arranged. The transfer paper P on which the toner image has been transferred is
After being separated from the photosensitive drum 1, the sheet is conveyed to a fixing device 12, where a toner image on the surface is fixed, a desired print image is formed, and the image is discharged outside the image forming apparatus main body.

The reader unit 18 irradiates the original 15 placed on the original glass table 14 with light from an illumination lamp 16 and reflects the reflected light on a photoelectric conversion element (1-line CCD) 19.
The image is converted into an electric signal corresponding to the image information by forming an image on the top. Here, the reflected light from the original 15 illuminated by the illumination lamp 16 is reflected by mirrors 17a, 17b, 1
The photoelectric conversion element 19 is guided by the lens 17d and guided by the lens 17d.
Imaged on top. The electric signal output by the photoelectric conversion element 19 is A / D converted by an A / D converter 21 to be 8-bit digital image data, and thereafter, the luminance signal is converted into density information by a black signal generation circuit 22. Is converted to image density data by the binarization circuit 23.

[0005] The 8-bit digital image data signal generated as described above is input to a laser drive circuit 24. The laser drive circuit 24 is a well-known PWM circuit, and operates in accordance with the magnitude of the input image density signal. Semiconductor laser 20
The light emission time to be n / off is modulated.

For example, as shown in FIG. 4, when image data for each pixel is inputted in the scanning direction of the laser as shown in FIG. 4A, the drive signal for turning on / off the laser is as shown in FIG. ing. That is, the on-duty of the laser drive signal when the image data is 00 hex is set to 5% of one pixel scan time, and the on-duty of the laser drive signal when the FF hex is set to 85% of one pixel scan time. In this way, shading is realized by performing area gradation within one pixel.

FIG. 6 shows general IL characteristics (driving current-light amount characteristics) of the laser.
The driving current used at the time of off is Ion / Io
ff, the laser drive current for the image signal in FIG. 4 is as shown in FIG. 4C, which is the current for driving the laser by the PWM circuit.

The laser driving method is roughly classified into the PWM circuit described above and a binary laser driving circuit. PW
As described above, the M circuit modulates a pulse width signal corresponding to the emission time of the semiconductor laser according to the magnitude of the input image density signal, while the binarization circuit modulates the pulse width signal according to the pixel size. The signal is converted into a two-stage signal of the specific on light emission signal and the off signal, and is input to the laser drive circuit 24 to turn on / off the laser (semiconductor laser element) 20. As a typical binarization method, there is a method of generating a binarized signal based on image data by a method such as an error diffusion method or a dither method. Is constant regardless of The difference is that a low density pixel emits a laser with a low probability, and a high density pixel emits a laser with a high probability.

As described above, the laser light driven and emitted according to the image signal is raster-scanned and written on the photosensitive drum 1 via the polygon mirror scanner 28 and the mirror 17f which rotate at a high speed, and a digital electrostatic latent image is formed as image information. Form.

Conventionally, electrophotography has been disclosed in US Pat. No. 2,297,961 and Japanese Patent Publication No. 42-23910.
Numerous methods are known as described in Japanese Patent Publication No. JP-B-43-24748 and Japanese Patent Publication No. 43-24748. Generally,
An electric latent image is formed by various means on a photosensitive drum, which is a recording medium using a photoelectric material, and then the latent image is developed using a toner (developer). The toner image is transferred onto a transfer material such as paper, and the toner image is fixed to the transfer material by heating or solvent vapor to obtain a copy image.

There are also known various developing methods for visualizing an electric latent image using a developer. For example,
Many methods such as a magnetic brush developing method described in U.S. Pat. No. 2,874,063, a powder cloud method described in 221 and 776, a fur brush developing method, a liquid developing method, and the like. There is a way. Among these developing methods, a magnetic brush developing method using a two-component developer mainly composed of a toner and a carrier has been widely put into practical use. However, this method is relatively stable, and a good image can be obtained. Of the two-component developer, such as deterioration of the toner and fluctuation of the mixing ratio of the toner and the carrier.

In order to avoid such drawbacks, various developing methods using a one-component developer consisting of toner alone have been proposed. According to this developing method, there is no need to control the mixing ratio of the toner to the carrier, and thus there is an advantage that the apparatus is simplified.

In the above-described one-component developing method, it is difficult to apply a charge to the toner because no carrier is used. For this reason, various methods for charging the toner have been studied.

For example, JP-A-50-4539 discloses that
Japanese Patent Laid-Open Publication No. Sho 54-2100 discloses a method of providing a charge by frictional charge with a toner carrier, and a method of providing a charge by frictional charge with a friction member provided in JP-A-54-2100. ing. Further, a method of applying a voltage to the friction member, a method of charging the toner with a charging member such as corona charging, and the like have been devised.

Conventionally, as a transfer path of a transfer material,
The transfer material forms a desired print image and is discharged to the outside of the image forming apparatus main body. However, there is only a transfer path to a discharge tray, a sorting device, a double-sided or a multiple-printing transfer device, or the like.

[0016]

According to the prior art described above, in a system having a means for transporting a transfer material without retaining a plurality of fixed transfer materials (hereinafter referred to as a "through-pass double-sided transport system"). The transfer material heated to about 200 ° C. in the fixing reaches the paper feeding process again within a short time such that heat is not completely radiated, and reaches the transfer position (transfer portion) via the transfer conveyance member. Becomes That is, compared to the case where the transfer material is fed from the transfer material feeder, the re-feeding by the through-pass double-sided conveyance causes more heat diffusion and influence. Particularly, in an apparatus capable of forming a high-speed image with a long life, the transfer material comes into contact with the transport roller while maintaining a high heat of about 50 to 100 ° C., and the feed roller and the transport roller for supplying and transporting the transfer material are used. Deposits from the rubber material may be offset on the paper and transported to the photoreceptor, where they may re-adhere to the photoreceptor surface. When the coating absorbs moisture in the air and absorbs moisture, the surface resistance of the photoreceptor decreases, and the charge of the electrostatic latent image after exposure including image information data cannot be completely retained. The image is disturbed and disturbs a part (corresponding to a paper feed roller or a transport roller) or the whole of the image information, and as a phenomenon on the image, the image flows as if the aqueous ink had flowed into the water.

When a corona charging method is used as a primary charging method on the photoreceptor, ozone generated by corona discharge and nitrate as a discharge product form a film on the photoreceptor. Image deletion occurs in the same manner as the adhered substance, but is mixed with the above-mentioned adhered substance and laminated, resulting in an even more deteriorated image deletion. The same applies to a post charger, a transfer charger, and a separation charger.

Conventionally, there has been adopted a method for improving the polishing effect on the surface of a photoreceptor by applying a developer to a photoreceptor and supplying the developer to a cleaning device to solve the problems described above. As for the supply timing, it is necessary to supply in a state other than image formation, and it is necessary to take the maximum time for polishing after the supply. However, in order to take a sufficient polishing time, there is an obstacle that the preparation time for starting the image forming apparatus becomes extremely long. Also,
A method of sucking and discharging ozone gas by sucking air from the inside of the shield case of each charger with a fan has been implemented, but it is not possible to completely discharge the gas, and the photosensitive material is exposed to the substance adhering to the photoreceptor surface. The adverse effect on the body could not be prevented, and the image deletion could not be completely suppressed.

In particular, when an a-Si photoreceptor is used in a high humidity environment as a photoreceptor, the generation of ozone due to discharge increases over a long period of use. An object adheres to the surface of the photoreceptor and absorbs moisture, so that an image in a flowing state is generated as an initial image after the power of the image forming apparatus is turned on.

Further, when laser or LED spot exposure writing is performed by digital data on the photoreceptor, this phenomenon of image deletion becomes remarkable. Spot diameter 50-70 when laser spot size is 600 dpi
In the case of μm, small dots are formed, so even small disturbances of electric charge are visually integrated as an aggregate and recognized as a difference from the normal part, so they are more noticeable, and they are evident as intense image deletion phenomena It will become.

In the developing method, an electric field flying developing method using a one-component magnetic developer mainly utilizing an electric field developing phenomenon, and in a jumping developing method, a disturbance of an electrostatic latent image on a photoreceptor is faithfully reproduced as it is. In particular, when starting up the image forming apparatus in a high humidity environment, the developer absorbs moisture while standing and the surface resistance of the developer particles decreases,
Since the charge amount to be held by the developer cannot be maintained, the developing efficiency is slightly reduced, and there is a problem that the density reduction and the image deletion phenomenon are more easily recognized. This obstacle becomes worse as the reproducibility of the minute dots decreases in accordance with the moisture adsorbed on the developer particles. That is, the obstacle occurs as a decrease in density or deterioration of image flow in accordance with humidity or the amount of water in the air.

The present invention has been made in view of the above circumstances, and even when the amount of water in the surrounding environment changes,
It is an object of the present invention to provide an image forming apparatus that prevents image deletion.

[0023]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: charging means for uniformly charging the surface of an image carrier; and charging means for charging the surface of the image carrier after charging. Exposure means for exposing in accordance with image data to form an electrostatic latent image, developing means for attaching toner to the electrostatic latent image and developing it as a toner image, and a toner image formed on the image carrier An image forming apparatus comprising: a transfer unit for transferring to a transfer material; a fixing unit for fixing a toner image on the transfer material; and a cleaning unit for cleaning the surface of the image carrier after the transfer of the toner image. A moisture detecting unit for detecting a moisture amount, and a control unit for controlling an image forming operation, wherein the control unit detects that the moisture detecting unit detects that the moisture amount of the surrounding environment is equal to or more than a specific moisture amount. Image formation for a specific number of times Immediately after the image area after being counted, by operating with the charging means and the exposure means and the cleaning means, to form a toner image on a ZoTanji body, characterized in that.

According to a second aspect of the present invention, there is provided the image forming apparatus of the first aspect, further comprising means for converting the multivalued image data into binary data.

According to a third aspect of the present invention, there is provided the first or second aspect.
In the image forming apparatus, based on the tone density reproduction characteristics in the image forming unit detected by the density characteristic detecting unit,
The image processing apparatus further includes a correction value creating unit that calculates an intermediate density between the detected densities of the black image data level and the white image data level, and uses the calculated value as a target density to correct the image data.

The present invention according to claim 4 is based on claims 1, 2,
Alternatively, in the image forming apparatus according to the third aspect, the control unit may include a toner black band width and an image for forming a black band, which are toner images formed on the image carrier, in accordance with the amount of water detected by the water detecting unit. Controlling write data.

According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the water detecting means detects the amount of water in the air.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the specific water content is 9 g / m ^3.
That is the feature.

The present invention according to claim 7 is based on claims 1, 2,
In the image forming apparatus of any one of 3, 4, 5, or 6, the charging unit is configured to provide a charge output value equivalent to that used in the previous image formation immediately after the image formation area after the specified number of image formations has been counted. And charging the toner image to be longer than a length corresponding to a circumferential length of the toner image formed on the image carrier.

The present invention according to claim 8 is based on claims 1, 2,
In the image forming apparatus according to any one of 3, 4, 5, 6, and 7, the exposing unit is configured to control an axis of a toner image to be formed on the image carrier immediately after an image forming area after a specified number of image forming operations is counted. Exposure equal to the length corresponding to the direction length,
The axial length of the toner image is shorter than the maximum exposure length at both ends in the longitudinal direction and is equal to or greater than the standard image forming area.

The present invention according to claim 9 is based on claims 1 and 2
In the image forming apparatus of 3, 4, 5, 6, 7, or 8,
The image carrier is a photosensitive drum in which a photoconductor for forming an electrostatic latent image is formed in a thin layer on a cylindrical conductive substrate.

According to a tenth aspect of the present invention, in the image forming apparatus of the ninth aspect, the photosensitive drum uses an a-Si photosensitive member.

According to an eleventh aspect of the present invention, in the image forming apparatus of the ninth or tenth aspect, the exposing means is a minute point exposing means, and scans and exposes a laser beam capable of digital exposure for each pixel. An electrostatic latent image is formed on the surface of the image carrier.

According to the twelfth aspect of the present invention, there is provided a ninth aspect of the present invention.
In the image forming apparatus of 0 or 11, immediately after the image forming area after the specified number of image forming operations has been counted, the exposing unit performs the black-out operation with the same laser lighting output value as that used in the previous image forming operation. The image data level exposure is performed, and the exposure is performed in the same manner as the length corresponding to the circumferential length of the toner image formed on the image carrier.

According to a thirteenth aspect of the present invention, in the image forming apparatus according to the ninth or tenth aspect, the exposing means drives the plurality of light emitting elements arranged in the main scanning direction to expose the image forming apparatus. Forming an electrostatic latent image on the surface of the carrier.

The present invention according to claim 14 is based on claim 1,
2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
Alternatively, in the image forming apparatus according to the thirteenth aspect, the developing means uses a one-component developer.

According to a fifteenth aspect of the present invention,
2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
In the image forming apparatus according to the thirteenth or fourteenth aspect, the developing unit develops the image with a developing bias output value equivalent to that used in the previous image forming immediately after the image forming area after the specified number of image forming operations is counted. And developing the toner image to the same length as the circumferential length of the toner image formed on the image carrier.

[0038]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG.
This is a laser beam printer (hereinafter referred to as "image forming apparatus"), and FIG. 1 is a longitudinal sectional view showing a schematic configuration thereof.

The image forming apparatus shown in FIG. 1 includes a drum type electrophotographic photosensitive member (hereinafter, referred to as "photosensitive drum") 1 as an image carrier. The photosensitive drum 1 is provided with a photoconductive layer (photoconductor for forming an electrostatic latent image) on a cylindrical conductive base, and is rotatably supported in the direction of arrow R1 in the figure. Around the photosensitive drum 1, a scoro-to-cone charger (primary charger) 2 for uniformly charging the surface of the photosensitive drum 1 is read in order along the rotation direction, an original is read, and an image signal proportional to the density of the image is read. An exposure device (micropoint exposure means) 3 for exposing the photosensitive drum 1 based on the image and forming an electrostatic latent image, a developing device 7 for attaching toner to the electrostatic latent image and developing it as a toner image, A developer charge control charger (hereinafter referred to as “post-charger”) 62 for adjusting the charge of the toner image of the toner image on the drum 1 so as to increase the transfer efficiency is provided. In addition, a transport system that transports the transfer paper (transfer material) P to the transfer unit is provided. Then, a corona transfer charger (transfer charger) 8 as a transfer device for transferring the toner image formed on the photosensitive drum 1 onto the transfer paper P, and separates the transfer paper P on which the toner image has been transferred from the photosensitive drum 1. Electrostatic separation charger (separation charger)
9. A cleaning device 13 for removing residual toner remaining on the photosensitive drum 1 after transferring the toner image, a pre-exposure lamp 30 for removing residual charges on the photosensitive drum 1, and the like are arranged. The transfer paper P on which the toner image has been transferred is
After being separated from the photosensitive drum 1, it is conveyed to a fixing device 12, where the toner image on the surface is fixed, a desired print image is formed, and the print image is discharged outside the image forming apparatus main body 101.

The reader section 18 irradiates the original 15 placed on the original glass table 14 with light from an illumination lamp 16 and reflects the reflected light on a photoelectric conversion element (1-line CCD) 19.
The image is converted into an electric signal corresponding to the image information by forming an image on the top. Here, the reflected light from the original 15 illuminated by the illumination lamp 16 is reflected by mirrors 17a, 17b, 1
The photoelectric conversion element 19 is guided by the lens 17d and guided by the lens 17d.
Imaged on top. The electric signal output by the photoelectric conversion element 19 is A / D-converted by the A / D converter 21 to obtain 8-bit digital image data.
In order to convert the luminance information into density information, the black signal generation circuit 22 performs log conversion to obtain image density data.

The image density data (8
The digital image data signal (bit) is converted into a two-stage signal of an on-light emission time of a specific on-time according to a pixel size and an off signal via a binarization circuit 23, and is input to a laser drive circuit 24, and converted into a drive current After the dot reproducibility correction is applied, the semiconductor laser is turned on / off at the drive signal timing binarized by the error diffusion method according to the magnitude of the input image density signal.

In the present embodiment, the binarization circuit 23 is realized by the error diffusion method, but may be of course a dither method or another method. Further, the laser drive circuit 24 may employ a method of modulating the on / off emission time of the semiconductor laser according to the magnitude of the input image density signal after the dot reproducibility correction is applied to the drive current by a well-known PWM circuit.

For example, as shown in FIG. 5, the laser lighting of binary image data will be briefly described. When image data for each pixel is input in the laser scanning direction as shown in FIG. The drive current to be turned off is as shown in (b). The drive current is turned on for a fixed time with a constant drive current regardless of the image data. And the exposure density in the plurality of pixel regions is modulated. That is, the number of times the laser drive signal is turned on when the image data is 00 hex is set to 0% of the lighting pixel ratio to the total number of pixels in a specific plurality of pixel regions, and the number of times the laser drive signal is turned on when the FF hex is set is For example, the lighting pixel ratio is set to 100% of the total number of pixels in a specific plurality of pixel regions. However, even at 0% of the lighting pixel ratio, a constant drive current flows as a bias current, and light emission is slight. In this manner, shading is realized by performing area gradation in a specific plurality of pixel regions.

As shown in FIG. 4, it is of course possible to use a PWM method. When the image data for each pixel is input in the scanning direction of the laser as shown in (a), the drive signal for turning on / off the laser is as shown in (b). That is, when the image data is 00 hex, the on-duty of the laser drive signal is set to 5 pixels per one pixel scan time.
%, And the on-duty of the laser drive signal at the time of FFhex is set to 85% of one pixel scan time. In this way, shading is realized by performing area gradation within one pixel.

FIG. 6 shows a general IL characteristic (driving current-light amount characteristic) of the laser.
The driving current used at the time of off is Ion / Io
ff, the laser drive currents corresponding to the image signals in FIGS. 5 and 4 are as shown in FIGS. 5B and 5C, respectively, which correspond to the binarizing circuit 23, the PWM circuit (not shown) and the laser circuit shown in FIG. This is a current for driving the laser 20 via the drive circuit 24. At this time, Ioff is not 0 mA,
By setting it slightly smaller than Itrehold,
It is known that the rise of the amount of light when the laser is on is improved.

Here, a 680 nm visible light laser is used as the laser.

As described above, the laser beam driven and emitted according to the image signal is raster-scanned and written on the photosensitive drum 1 via the polygon mirror scanner 28 and the mirror 17f rotating at high speed, and a digital electrostatic latent image is formed as image information. Form.

In this embodiment, an amorphous silicon drum is used for the photosensitive drum 1. Amorphous silicon drum has high stability and high durability on the conductive base,
It has the feature of long life. The a-Si photoreceptor, which has a long life, high-speed output, and has a surface layer SiC hardening type, and has a high photosensitivity in the photosensitive layer, has a high charge retention ability and almost no scattering of irradiation light by the surface layer. Since the minute electrostatic latent image at the minute spot exposure portion is held without charge diffusion, a minute latent image of 600 dpi, 1200 dpi, or the like is faithfully formed, and a high-definition latent image is formed.

FIGS. 2A to 2C show respective steps for explaining the image forming process of the present embodiment. In each figure, the relationship between the surface potential of the photosensitive member and the developing bias is schematically shown. I have.

In (a), the photosensitive member is charged with a corona charger by +
It is uniformly charged to 420V.

In (b), image information is exposed, and the surface potential of the image information exposed portion is attenuated to +50 V to form an electrostatic latent image. Since the image exposure is a pulse width modulated light amount as described above, the actual photosensitive drum potential after exposure is, in principle, only the potential of the laser off part and the potential of the laser on part. In a general non-contact surface voltmeter that measures the integrated potential in a sufficiently large area with respect to the spot diameter of the spot, it is apparently measured as a halftone potential. That is, even in the non-image portion (image data 00hex) of the image region, since the slight exposure is performed as described above, the surface potential is attenuated to +400 V, and the image portion of one image region (image data FFhex). At, the surface potential attenuates to +50 V to form an electrostatic latent image.

Next, at (c), a developing bias voltage (for example, DC DC +2 is applied to AC AC) is applied to the sleeve of the developing device.
80V superimposed. The DC component is indicated by a broken line. )
Is applied to reversely develop the exposed portion. Here, the developing unit uses a well-known one-component magnetic toner to perform development without contacting the photoconductor.

An image streak prevention sequence based on detection of a high humidity environment, which is a feature of the present invention, is shown below. The following summarizes each condition of the sequence for each purpose.

Example 1 Post-rotation toner black belt in high humidity detection ・ Purpose: Measures to eliminate flowing material (sharpening) to prevent image bleeding ・ Outline: The environment sensor detects more than a specific amount of water and determines that the environment is high humidity, and forms a specific number of images After counting, the drum is rotated, the developing device and the cleaner system are rotated by the subsequent rotation, and primary charging, laser exposure, and development are performed on the drum during the rotation to form a solid black belt. -Conditions: 1) High humidity judgment: moisture 9 g or more. (As a guide, NN23
2) Idling time: Assuming that copying / printing is performed after solid black, use it as a substitute for idling. That is,
It has no special idling time. However, the time for the solid black to reach the cleaning blade is the lower limit, and the rotation time is as long as possible within the design range. 3) Primary charging: Output with the same control value as the image area (default output when there is no data). The output time is equivalent to the black band width. 4) Laser: Output with the same power control value as the image area (default output when there is no data). FFhex solid image area. The output time is equivalent to the black band width. 5) Development: Output with the same DC control value as the image area. AC + D
C (default output when there is no data). The output time is equivalent to the black band width. DC values can be entered. Black belt density can be changed. The developing AC is also used by the separation claw AC, and is ON until the black band passes through the separation claw. 6) Black belt: length in the sub-scanning direction: 40 mm on the drum surface. Can be entered. Main scanning direction length: Nominal width of A3 width in image area center distribution. Lateral registration tolerance (correction intersection of longitudinal transfer paper edge deviation)
Not included. Timing: Post-rotation at the end of the job after the specified number of copies and prints has been counted or during pre-rotation of the next job (in the case of pre-rotation, move away from the image area by more than the sheet interval). Specified number of intervals: Every 200 sheets by default. Can be entered. (In the experiment, the effect of preventing and eliminating streaks was confirmed with a post-rotation black belt of 20 mm width every 200 sheets.)

Example 2 A combination system of the morning black belt at HH, JJ, and NL + idle rotation and the post-rotation black belt for each HH specific number of sheets.・ Purpose: Measures to eliminate flow material (sharpening) by image flow countermeasures ・ Summary: In the morning, when the environment is in the following moisture content area,
In the preparation stage of image formation, the drum rotation, the developing device, and the cleaner system also rotate under the following conditions, and during the rotation, primary charging, laser exposure, and development are performed on the drum to form a toner solid black band, and When the sensor detects a specific amount of water or more and determines that the environment is high humidity, after counting the number of image formation of the specified number of sheets, the drum rotates, the developing unit, and the cleaner system rotate, and the primary charging is performed on the drum. , Laser exposure and development to form a solid black band. a) Black belt in the morning with toner plus idle rotation and post-rotation black belt at every specific number of sheets counted: moisture content W ≧ 9 g b) Rotation in the morning: moisture content 9 g> W ≧ 5 g c) Normal pre-multiple rotation only: moisture content 5 g Less than the idle rotation of the drum, the developing device, and the cleaner system also idle according to the moisture content area, and at the same time as the start of the idle rotation, primary charging, laser exposure and development are performed on the drum to form a toner black band. .・ Conditions: 1) Judgment in the morning: the temperature of the fixing thermistor when the main switch is ON is 100 ° C or less. 2) Environmental judgment: a) Black belt in the morning with toner + idle rotation and post-rotation black belt after counting of a specific number of sheets: moisture content W ≧ 9 g (as a guide, NN 23 ° C., 60
% Is 10.5 g of water content) b) One rotation in the morning: 9 g of water content> W ≧ 5 g c) Normal multi-rotation only: less than 5 g of water content 3) Idle rotation time: a) Black belt of toner and free rotation in the morning : From immediately after HH determination to fixing thermistor temperature 195 ° C. Approximately 4.5 minutes (the rotation time varies depending on the fixing thermistor temperature at the start of idling). -Post-rotation black belt: Assuming that copying / printing is performed after solid black, use it as a substitute for idle rotation. That is, no special idle rotation time is provided. However, the time for the solid black to reach the cleaning blade is the lower limit, and the rotation time is as long as possible within the design range. 4) Primary charging: Output with the same control value as the image area (default output when there is no data). The output time is equivalent to the black band width. 5) Laser: Output with the same power control value as the image area (default output when there is no data). FFhex solid image area. The output time is equivalent to the black band width. 6) Development: Output with the same DC control value as the image area. AC + D
C (default output when there is no data). The output time is equivalent to the black band width. DC value can be input and black belt density is variable. 7) Black belt: length in the sub-scanning direction: black belt 40 on the drum surface
0mm, rear rotating black belt 20mm. Black belt width can be entered. Main scanning direction length: Nominal width of A3 width in image area center distribution (excluding horizontal registration tolerance) Timing: Asaichi black belt is in front multiple rotation. The post-rotation black band is post-rotation at the end of the job after the specified number of copies and prints has been counted up or during pre-rotation of the next job (in the case of pre-rotation, it is more distant from the image area than the image area). Post-rotation black belt interval specific number: every 200 sheets by default. Can be entered.・ Effects: Flow and streak flow are 400mm in the morning, 4.5 minutes in idle rotation, and approximately 200mm in the post-rotation black belt every 200 sheets, and the effect of eliminating streak flow is confirmed.

Here, the operation of Example 1 of the present embodiment will be described step by step with reference to FIG.

When the environment is a specific moisture content region, the moisture content W ≧ 9
When it is detected as g, it is determined that the environment is a high humidity environment (a). The 200th copy is assumed to be a copy start when the default number of copies (specified number of intervals) of the total number of copies and prints is 200. It detects that the specified number of sheets has been reached, and operates to perform the post-rotation black band during post-rotation at the end of this job. After the laser exposure of the image area is completed, the drum drive motor is operated to keep the drum idling, and at the same time, the developer drive motor is operated to rotate the sleeve of the developer, and at the same time, the cleaner drive motor (main motor) is operated. Then, the cleaner system also idles. Further, the polygon mirror rotation drive of the laser scanning system continues its operation.

The primary charging is also performed continuously, and the amount of charge is output using the same control value as that of the image area, that is, the potential control value at the closest time. If there is no previous data, output is performed with the program default value. The output extension time is equal to or longer than the black band width, and has a slightly extra charged area before and after the black band. In total, this is a time corresponding to 20 mm or more in the circumferential direction on the drum. The length in the main scanning direction is equal to or greater than the nominal width of A3 width in the image area center distribution.

Next, in the laser exposure, the image area is completed, the light is turned off for a specific time, and then the lighting for the black band is performed. The laser is turned on with the same power control value as in the image area.
If there is no such data, output is performed with the program default value. FF for image area as image data level
hex solid. The length in the main scanning direction is a nominal width of A3 width in image area center distribution. In other words, laser beam scanning is performed with a width that does not include the adjustment tolerance for registration in the main scanning direction (lateral registration). Here, the 297 mm image area FFhe
x output is performed. The output time is a time corresponding to the black band width, and here is a time corresponding to 20 mm in the circumferential direction on the drum. Also, before outputting the FFhex, a bias current is applied to make the laser output slightly rise in order to speed up the rise of the laser output. The output data is not limited to FFhex, but may be 80hex or 40hex depending on the state of the image forming apparatus.
x may be used.

Next, in the development, an AC voltage + DC voltage is output. The AC voltage is output at a standard voltage, and the DC voltage is output at a DC control value similar to the image area. In the present embodiment, the black band width is its DC control value of 280 V. However, a DC control value of 300 V for the non-image area is output so as to completely cover the area where the primary charging before and after the black band width is output. The setting is such that reversal development in the area of only primary charging is minimized. FIG. 21 shows only the DC voltage, but the AC voltage is
On in the area that further covers the slope of the voltage (for non-image)
are doing. If there is no previous data, a DC control value is output with a program default value. The output time is equivalent to the black band width, and here, 20 times in the circumferential direction on the drum.
It is a time equivalent to mm. The DC value is set so that it can be input on the scanning panel and the black band density can be changed.

After the toner band has been formed on the drum, the black toner band is carried to the drum cleaning device and is stopped by the edge of the cleaning blade, where the accumulated toner removes the layered material on the drum surface. Since this scraping effect is proportional to the rubbing time, the time should be as long as possible to secure as long as possible.

In the above black band formation, the black band data of the post-rotation black band is controlled (the black band width is fixed) according to the detected moisture amount as shown in FIG. By fixing the black belt image data, it is possible to supply the black belt toner to the most appropriate cleaning blade according to the environmental humidity, and the effect of the moisture absorbing substance on the drum affecting the image according to the environmental moisture amount Since it is possible to supply the toner according to the degree, it is possible to avoid wasteful toner consumption due to excessive toner black band in a relatively low moisture content even in a high humidity environment. Conversely, when the water content is extremely high, by supplying more toner, it is possible to control so as to sufficiently remove the moisture absorbing portion of the surface layer of the attached moisture absorbing substance. The selection of the control content is variable depending on the usage status of the image forming apparatus. In particular, it is desirable that the larger the number of sheets used during the specific period is, the larger the black band width is, and the selection is made so as to remove a large amount of the hygroscopic substance adhered. As a result, it is possible to appropriately cope with any environmental humidity range, and to always provide a good image.

As described above, the most severe humid environment against image flow (water content per unit volume of cubic meter is 9
g / m ³ or more), the image forming apparatus can obtain a good image over a long period regardless of the environment.

Hereinafter, a method of correcting unevenness in the main scanning direction when density unevenness occurs in the developing device 7 and other portions will be described in detail.

FIG. 7 is a schematic diagram showing a cause analysis of the cause of the occurrence of density unevenness in the main scanning direction. The vertical axis indicates the surface potential on the photosensitive drum, and the horizontal axis indicates an arbitrary position in the main scanning direction.

(A) shows the potential at a place where the charging potential is normally obtained at the target potential of 400 V and at the place where the charging potential is smaller than the target potential. This is because the charging ability characteristic of the photosensitive drum 1 is different from the characteristic of the surface potential obtained on the photosensitive drum 1 with respect to the current applied to the corona wire of the primary charger 2 as shown by the three types of characteristic curves in FIG. This is the surface potential unevenness that occurs. Even if the charging ability characteristic of the photosensitive drum 1 is uniform, if the charging ability of the primary charger 2 is not uniform depending on the position in the main scanning direction, surface potential unevenness occurs.

FIG. 7B shows the potentials at a place where the potential is normally obtained at the target potential of 50 V of the exposure part and at a place larger than the target potential, although the surface potential formation by the charging is performed uniformly. I have. This is the surface potential unevenness generated due to the difference in the photosensitivity characteristics of the photosensitive drums 1 as shown by the three types of characteristic curves in FIG. Also, the photosensitive drum 1
Even if the photosensitivity characteristics are uniform, if the light irradiation amount is not uniform depending on the position in the main scanning direction, surface potential unevenness occurs.

FIG. 7 (c) shows that although the surface potential formation by charging and the surface potential formation by exposure potential decay were performed uniformly, the position where development was normally performed at the exposed portion potential of 50 V and the target were compared. Also shows a small place. This is Figure 1
As shown by three characteristic curves of 0, the surface potential of the photosensitive drum 1 and the application D
This is density unevenness caused by a difference in developing ability with respect to a developing contrast, which is a difference between C voltages. This occurs when the charging characteristics of the density unevenness are non-uniform in the main scanning direction, or when the gap between the photosensitive drum 1 and the developing sleeve is non-uniform depending on the position in the main scanning direction.

There is also non-uniform density due to non-uniformity in the main scanning direction of transfer efficiency at the time of transfer and separation (not shown).

Here, all the causes of unevenness are comprehensively detected from the output printout image and corrected.

FIG. 12 is a flowchart showing an outline of the flow of the correction operation.

Step (S1) The image forming apparatus of this embodiment has an "improving image mode" as an image unevenness improvement mode in the input interface, and the mode is first started.

Step (S2) Next, an axial unevenness (unevenness in the main scanning direction) correction mode is selected.

Step (S3) The key for starting the axial unevenness correction mode is pressed to start.

Step (S4) The image forming apparatus outputs a test image sample as shown in FIG. Conditions for forming this sample include:
In order to form an image of completely solid black, halftone halftone, solid white, and the like, three types of image exposure conditions (F0, 80 in FIG. , 00 hex), developing, transferring and fixing under the above-mentioned developing conditions, outputting a sample, and detecting the gradation density reproduction characteristic by a density characteristic detecting means (not shown).

Step (S5) The output sample is placed at a specific position on the platen by the mode executor in the paper passing direction and the front or rear side, and the placement is completed by document recognition means (not shown). Is detected.

Step (S6) When it is determined that the loading is completed, the original is read by the reader as described above. Reading by this reader is 400-60
It is desirable to read at a resolution of about 0 dpi.

Step (S7) It is determined whether or not the original is a test image sample based on whether or not the density gradation is the same pattern. If it is determined that the sample is not a test image sample, an error is notified in step S11, and the process ends. In this case, step S
5 processing may be returned.

Step (S8) If it is determined that the sample is a test image sample, the axial density distribution is calculated as shown in FIG. When a test image sample is formed with PWM levels of F0, 80, and 00 hex, the read density distribution of the halftone portion of 80 hex where unevenness is most easily detected is calculated (F0, 8).
The density distribution may be calculated for each of 0 and 00 hex. ).

Step (S9) When the target density is set to 0.5 in FIG. 13B, the increase / decrease of the read density distribution of the halftone portion with respect to 0.5 corresponds to each pixel in the main scanning direction. Is calculated. When the minus correction is represented by a negative sign and the plus correction is represented by a plus sign, the required correction density becomes as shown in FIG.
Is a diagram of the required correction density as if the polarity were inverted.

Step (S10) The correction light amount (correction level) for each pixel of the dot exposure laser is determined from FIG. As an example, when the required correction density is +0.8 in FIG. 14, the surface potential is -200 V, the photosensitive drum surface light quantity is +0.25 μJ,
This indicates that the correction of +80 hex is required in the image data. A correction amount level corresponding to each pixel in the main scanning direction is assigned by this capacity, and a correction table is created. Here, this mode ends, and the operation panel, which is the input interface unit of the image forming apparatus, returns to the normal copy or print mode.

When the correction amount corresponding to each pixel position in the main scanning direction is determined in this way, it is stored in a correction table in the main scanning unevenness correction circuit 50 (see FIG. 1) as a correction value creating means. .

FIG. 20 shows a specific circuit configuration of the main scanning unevenness correction circuit 50 in the present embodiment.

The illustrated correction table 101 and adder 10
4. The main scanning unevenness correction circuit 50 includes the selector 102, the address generation circuit 103 and the selector 102. CPU 100
Is a control means for controlling the entire apparatus, and a ROM for storing a control program as a copying machine, a program according to the flowchart of FIG. 12 described above, and a work area therein. It has a RAM to be used.

In the configuration shown in FIG.
Has a capacity of at least the number of pixels in the main scanning direction (9 bits per pixel, 1 bit of which is plus or minus sign bit). Then, as described above, the correction data of each pixel generated based on the image data obtained by reading the test image sample is written to a corresponding address position of this correction table (configured by the RAM). Therefore, the CPU 100 outputs to the selector 102 a signal for supplying the address from the CPU 100 to the correction table 101, and outputs an address, data to be written, and a write signal to the correction table 101. When the writing of the correction data to all the pixel positions in the main scanning direction is completed in this manner, a signal for selecting an address from the address generation circuit 103 is output to the selector 102, and a read signal is output.

The address generation circuit 103 includes the photosensitive drum 1
Is triggered by a beam detect signal provided in the vicinity of the correction table 1 at a predetermined time, in synchronization with the carrier clock of the image data from the black signal generation circuit 22.
01 are sequentially output as address signals. As a result, the correction table 101 outputs the correction signal in synchronization with the image data (pixel data) from the black signal generation circuit 22. The adder 104 adds the data from the correction table 101 to the image data from the black signal generation circuit 22 and outputs the result to the binarization circuit 23. Since the correction table stores positive and negative correction data as described above, the adder 104 binarizes the image data obtained by correcting the characteristics of the image data in accordance with the characteristics of the printer engine. This is output to the circuit 23.

Although the description will be made before and after, the test image sample is formed by the CPU 100 every predetermined number of main scanning lines.
hex, 80 hex, and f0 hex are output in place of the black signal generation circuit 22. However, since the test image formation is performed to know the characteristics of the printer engine, no data is output from the correction table 101, or data of 0 is always output. In some cases, when forming a test image sample, 00, 80 hex, f0he
It is also possible to write x at an appropriate timing and output it. At this time, if the image reading is not performed, 0 data is output from the black signal generation circuit 22, so that the test image sample described above can be formed as a result. An advantage in this case is that a test image sample can be formed only with the configuration of FIG.

Since data such as image unevenness is corrected at the 8-bit multi-level signal stage using the above-described correction table 101, uniform data is formed at the time of binarization. In this example, the density unevenness is completely corrected, so that a high-quality image without the density unevenness in the longitudinal direction (main scanning direction) can always be provided. In particular, according to the present embodiment, it is possible to suppress density unevenness in a relatively low density portion (highlight portion).

When the present invention is applied to an apparatus for forming an image by the PWM method, the output of the adder 104 is D / A converted and compared with a triangular wave from a triangular wave generating circuit, as shown in FIG. A signal having a pulse width depending on the density may be generated and supplied to the laser drive circuit 24. The reason why the pulse width signal is generated even when the density is 0 is as described above. Note that the laser drive circuit 24 is driven to generate laser light for a time dependent on the pulse width of the pulse width modulation signal.

As described above, when the temperature of the fixing thermistor when the main switch is turned on is equal to or lower than the specific temperature and the environment is in the specific moisture amount region (hereinafter, the following range), it is determined that the environment is the morning and the high humidity environment (and each environment). Drum idle rotation (the developing unit and cleaner system also idle) according to the water content area, and at the same time as the start of idle rotation, primary charging, laser exposure, and development are performed on the drum to form a toner black band. By combining and correcting the density unevenness at the laser writing level using the correction table, the developability increases until the density is sufficient and the reproducibility of isolated dots can be sufficiently secured. Therefore, even in the first copy image in the morning in a high humidity environment, a high-quality image with no image deletion and high density and no density unevenness in the longitudinal direction (main scanning direction) is always obtained.

<Embodiment 2> FIG. 15 shows an image forming apparatus according to Embodiment 2 of the present invention. FIG. 1 is a longitudinal sectional view showing a schematic configuration of the image forming apparatus.

The photosensitive drum 1 is provided with a photoconductive layer on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. A primary charger (first scoroton-cone charger) that uniformly charges the surface of the photosensitive drum 1 around the photosensitive drum 1 in the rotation direction.
2. a first exposure device 3, which reads a document, exposes the photosensitive drum 1 based on a first image signal proportional to the density of one color image separated into two colors, and forms a first electrostatic latent image; A first developing device 4 for forming a first image by attaching toner to the first electrostatic latent image, and a recharger (second scorotron charger for charging the photosensitive drum 1 after carrying the first image) )
5. Second exposure for forming a second electrostatic latent image by performing exposure of an amount obtained by adding a certain exposure to the exposure based on the second image signal proportional to the density of the other color image that has been separated. Device 6,
A second developing device 7 for attaching a toner to the second electrostatic latent image to form a second image; a pre-transfer charger 62 for charging a color superimposed image formed on the photosensitive drum 1 before transfer; Corona transfer charger (transfer charger) 8 for transferring onto a transfer paper P, which is a material, and transferring the transfer paper P on which the color superimposed image has been transferred to the photosensitive drum 1
, A cleaning device 13 for removing residual toner remaining on the photosensitive drum 1 after transferring a color superimposed image, and a pre-exposure lamp for removing residual charge on the photosensitive drum 1 30 and the like are arranged.
The transfer paper P on which the color superimposed image has been transferred is a photosensitive drum 1
After being separated from the fixing device 12, the toner image is conveyed to the fixing device 12, where the toner image on the surface is fixed, a desired print image is formed, and the print image is discharged to the outside of the image forming apparatus main body.

Here, a connecting duct 61 is directly connected to the pre-transfer charger 62, and a blowing fan 60 is further connected thereto.

Further, the image scanner unit 18 illuminates the original 15 placed on the original glass table 14 with the illumination lamp 1.
6 for scanning and reading, and converting the image information into an electric signal by the photoelectric conversion element 19.
The reflected light from the original 15 scanned by the
The light is guided to a, 17b, and 17c, and is imaged by a lens 17d on a photoelectric conversion element 19 containing red, green, and blue filters. The electric signal from which each component of red, green, and blue is output by the photoelectric conversion element 19 is digitized by the A / D converter 21 and then sent to the signal processing unit 22 as a color separation unit to be sent to the red and black components. Is converted into an image signal proportional to the image density of each component.

Here, the image data is corrected for each pixel by the axial direction (main scanning direction) unevenness correction table 50 (see 50 in FIG. 17).

The red image signal (first image signal) and the black image signal (second image signal) are sent to laser drivers 24b and 24a as signal generators, and are supplied in accordance with the red and black image signals. Laser 20b, 20
The light emission of a is turned on / off. The laser light emitted in response to the red signal is used as first image information by a polygon mirror 2.
8. Write a first electrostatic latent image on the photosensitive drum 1 via the mirror 17e. The laser light emitted in an amount corresponding to the black signal writes a second electrostatic latent image on the photosensitive drum 1 via the polygon mirror 28 and the mirrors 17f and 17g as second image information.

In this embodiment, an amorphous silicon drum is used for the photosensitive drum 1. Amorphous silicon drums have features such as high durability and long life.

FIG. 16 illustrates the image forming process in the two-color image forming mode according to this embodiment.
(F) shows each step, and in each figure, the surface potential of the photosensitive drum 1 is schematically shown.

In (a), the photosensitive drum 1 is charged to, for example, +400 V by the corona charger 2, and then, in (b), the first exposure of image information is performed, and the surface potential of the exposed portion is set to, for example, +50 V. Attenuate to form a first electrostatic latent image.

Next, in (c), a developing bias voltage (for example, +300 V: indicated by a broken line) is applied to the developing sleeve of the first developing device 4 to reversely develop the exposed portion.

After the first development, recharging is performed in (d). A voltage of 600 V, which is higher than the desired second development position potential of 400 V, is applied to the grid of the recharger 5, and the first developed non-image portion is, for example, Control is performed to charge to 600V. At that time, the first developing unit is charged to, for example, 500V.

Next, when the exposure according to the second image information is performed in (e), a constant exposure amount (for example, the first developed non-image portion is attenuated by 200 V) over the entire surface as compared with the second developed single color. Exposure is large). At this time, in the first developing section, the exposure for the fixed exposure amount does not attenuate the potential attenuating in the first non-developing non-image section, but only attenuates, for example, 100V. This is because the first developer scatters the light without transmitting it, and its transmittance was 50%. The surface potential after exposure for the second exposure constant additional exposure amount of 0.25 μJ becomes the second development position target potential of 400 V. The first development non-image portion recharged target potential is represented by a straight line having a known drum sensitivity of 800 V / μJ. It was assumed that it was 600V. Next, also from the known toner layer transmittance of 50%, the amount of light reaching the drum to the first image developing unit is 0.125 μJ. The first method is similar to the method described above.
The target potential after recharging of the developed image portion may be set to 500V.

In this embodiment, a semiconductor laser is used as the second exposure means. However, no complicated processing is required between the second developing single-color mode and the two-color mode. Since the amount of laser light is determined by the laser drive current, a constant offset current is added to the drive current in the second development monochrome mode in the two-color mode. That is, the second image signal is also weakly exposed to the portion where the second image signal is off, and the portion where the second image signal is turned on is also subjected to the exposure that is increased by the same amount of exposure, the potential of the first developed image portion is 400 V, and the first developed image portion is 400 V. The potential of the non-image area is also 400
V, and when the second image signal is on, the first developed non-image portion is exposed to 50V. Thereafter, in the developing process, the second
By applying a bias of 300 V to the developing sleeve,
A sufficient second image density can be obtained without the second developer being mixed into the first developing portion or being developed in the non-image portions of the first and second images.

An image deletion prevention sequence based on detection of a high-humidity environment, which is a feature of the present embodiment, will be described below.
The operation is the same as in the first embodiment, and a description thereof will be omitted.

Here, the operation of this embodiment will be described step by step with reference to FIG.

When the environment is defined as a specific moisture content region, the moisture content W ≧ 9
When it is detected as g, it is determined that the environment is a high humidity environment (a). The 200th copy is assumed to be a copy start when the default number of copies (specified number of intervals) of the total number of copies and prints is 200. It detects that the specified number of sheets has been reached, and operates to perform the post-rotation black band during post-rotation at the end of this job. After the laser exposure of the image area is completed, the drum drive motor is operated to keep the drum idling, and at the same time, the developer drive motor is operated to rotate the sleeve of the developer, and at the same time, the cleaner drive motor (main motor) is operated. Then, the cleaner system also idles. Further, the polygon mirror rotation drive of the laser scanning system continues its operation.

The primary charging is also continuously performed, and the output is performed using the same control value as that of the image area, that is, the potential control value at the closest time as the charge amount. If there is no previous data, output is performed with the program default value. The output extension time is equal to or longer than the black band width, and has a slightly extra charged area before and after the black band. In total, this is a time corresponding to 20 mm or more in the circumferential direction on the drum. The length in the main scanning direction is equal to or greater than the nominal width of A3 width in the image area center distribution.

Next, in the laser exposure, the image area is ended, and the laser light is once turned off for a specific time, and thereafter, lighting for a black band is performed. The laser is turned on with the same power control value as in the image area.
If there is no such data, output is performed with the program default value. FF for image area as image data level
hex solid. The length in the main scanning direction is a nominal width of A3 width in image area center distribution. In other words, laser beam scanning is performed with a width that does not include the adjustment tolerance for registration in the main scanning direction (lateral registration). Here, the 297 mm image area FFhe
x output is performed. The output time is a time corresponding to the black band width, and here is a time corresponding to 20 mm in the circumferential direction on the drum. Also, before outputting the FFhex, a bias current is applied to make the laser output slightly rise in order to speed up the rise of the laser output. The output data is not limited to FFhex, but may be 80hex or 40hex depending on the state of the image forming apparatus.
x may be used.

Next, in development, an AC voltage + DC voltage is output. The AC voltage is output at a standard voltage, and the DC voltage is output at a DC control value similar to the image area. In the present embodiment, the black band width is its DC control value of 280 V. However, a DC control value of 300 V for the non-image area is output so as to completely cover the area where the primary charging before and after the black band width is output. The setting is such that reversal development in the area of only primary charging is minimized. FIG. 21 shows only the DC voltage, but the AC voltage is
On in the area that further covers the slope of the voltage (for non-image)
are doing. If there is no previous data, a DC control value is output with a program default value. The output time is equivalent to the black band width, and here, 20 times in the circumferential direction on the drum.
It is a time equivalent to mm. The DC value is set so that it can be input on the scanning panel and the black band density can be changed.

After the toner band has been formed on the drum, the black toner band is carried to the drum cleaning device and is stopped by the edge of the cleaning blade, where the accumulated toner removes the layered material on the drum surface. Since this scraping effect is proportional to the rubbing time, the time should be as long as possible to secure as long as possible.

In the above black band formation, the black band data of the post-rotation black band is controlled (the black band width is fixed) according to the detected moisture content as shown in FIG. By fixing the black belt image data, it is possible to supply the black belt toner to the most appropriate cleaning blade according to the environmental humidity, and the effect of the moisture absorbing substance on the drum affecting the image according to the environmental moisture amount Since it is possible to supply the toner according to the degree, it is possible to avoid wasteful toner consumption due to excessive toner black band in a relatively low moisture content even in a high humidity environment. Conversely, when the water content is extremely high, by supplying more toner, it is possible to control so as to sufficiently remove the moisture absorbing portion of the surface layer of the attached moisture absorbing substance. The selection of the control content is variable depending on the usage status of the image forming apparatus. In particular, it is desirable that the larger the number of sheets used during the specific period is, the larger the black band width is, and the selection is made so as to remove a large amount of the hygroscopic substance adhered. As a result, it is possible to appropriately cope with any environmental humidity range, and to always provide a good image.

As described above, the most severe humid environment (water content per cubic meter of 9
g / m ³ or more), the image forming apparatus can obtain a good image over a long period regardless of the environment.

Hereinafter, a method of correcting unevenness in the main scanning direction when the density unevenness occurs in the developing device and other portions will be described in detail.

A description will be given using the flow of operation for creating the correction table 50 shown in FIG. 12 as in the first embodiment.

(1) The image forming apparatus of the present embodiment has an “improving image mode” as an image unevenness improvement mode in the input interface, and the mode is started first.

(2) Next, an axial direction unevenness (main scanning direction unevenness) correction mode is selected.

(3) Press the key to start the axial direction unevenness correction mode and start.

(4) The image forming apparatus outputs a test image sample as shown in FIG. As the conditions for forming this sample, in order to form an image such as a completely solid black, a halftone halftone, and a solid white, three types of image exposure conditions obtained by the above-described primary charging conditions for forming the surface potential (see FIG. 11, F0, 80, and 00 hex), developed, transferred, and fixed under the above-described developing conditions to output a sample.

Here, as a feature of the present embodiment, a test image sample is output for each of two colors (for example, red and black). Thereafter, the following operations (5) to (10) are performed for each of red and black colors.

(5) The output sample is placed at a specific position on the platen by the mode executor at the leading end and the front or back side of the sample in the paper passing direction. Determine whether it has been detected.

(6) When it is determined that the loading is completed, the original is read by the reader as described above. It is desirable that the reading by the reader be performed at a resolution of about 400 to 600 dpi.

(7) It is determined whether or not this original is a test image sample based on whether or not the density gradation is the same pattern.

(8) If it is determined that the sample is a test image sample, the distribution of the density in the axial direction is calculated as shown in FIG. When a test image sample is formed at F0, 80, and 00 hex of the PWM level, the read density distribution of the halftone portion of 80 hex at which unevenness is most easily detected is calculated (the density distribution is calculated at F0, 80, and 00 hex, respectively). May be done.)

(9) As shown in FIG.
In the case of 5, the increase / decrease of the read density distribution of the halftone portion with respect to 0.5 is calculated so as to correspond to each pixel in the main scanning direction. If the minus correction is represented by a negative sign and the plus correction is represented by a plus sign, the required correction density becomes a required correction density as shown in FIG.

(10) The correction light amount (correction level) for each pixel of the dot exposure laser is obtained from FIG. As an example, in FIG. 14, the required correction density is +0.8.
In the case of, the surface potential is -200V and the drum surface light amount is + 200V.
This indicates that a correction of +80 hex is required for image data of 0.25 μJ. A correction amount level corresponding to each pixel in the main scanning direction is assigned by this capacity, and a correction table is created. Here, this mode ends, and the operation panel, which is the input interface unit of the image forming apparatus, returns to the normal copy or print mode.

As described above, when the temperature of the fixing thermistor when the main switch is turned on is lower than the specific temperature and the environment is in the specific moisture content region (below), it is determined to be the morning and the high humidity environment (and each environment). According to the water content region, the drum is idled (the developing unit and the cleaner system are also idled), and the primary charging, laser exposure and development are performed on the drum almost simultaneously with the start of the idle rotation to form a toner black band. And
In addition, by using a correction table to correct the density unevenness at the laser writing level, the developability has been increased until the density is sufficient and the reproducibility of isolated dots can be sufficiently ensured. Even in the first copy image in the morning in the environment, it is possible to obtain a high-quality two-color image with no image bleeding, high density, and constant density unevenness in the longitudinal direction (main scanning direction).

<Embodiment 3> FIG. 18 is a schematic structural view of Embodiment 3 of an image forming apparatus according to the present invention.

The photosensitive drum 11 is provided with a photoconductive layer on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. A scorotocon charger (primary charger) is provided around the photosensitive drum 1 to uniformly charge the surface of the photosensitive drum 1 in order along the rotation direction.
2. An exposure device 3 for reading an original, exposing the photosensitive drum 1 based on an image signal proportional to the image density, and forming an electrostatic latent image, attaching toner to the electrostatic latent image and developing the toner image as a toner image Developing device 7, post-charging device (pre-transfer charging device) 62 for charging the toner image before transfer, corona transfer charging for transferring the toner image formed on the photosensitive drum 1 onto transfer paper P as a transfer material (Transfer charger) 8, an electrostatic separation charger (separation charger) 9 for separating transfer paper P on which the toner image has been transferred from photosensitive drum 1, and remained on photosensitive drum 1 after transferring the toner image. A cleaning device 13 for removing residual toner, a pre-exposure lamp 30 for removing residual charges on the photosensitive drum 1, and the like are provided. The transfer paper P on which the toner image has been transferred is conveyed to the fixing device 12 after being separated from the photosensitive drum 1, where the toner image on the surface is fixed, and a desired print image is formed. Is discharged to the outside.

The reader section 18 irradiates the original 15 placed on the original glass table 14 with light from the illumination lamp 16 and reflects the reflected light on a photoelectric conversion element (1-line CCD) 19.
The image is converted into an electric signal corresponding to the image information by forming an image on the top. Here, the reflected light from the original 15 illuminated by the illumination lamp 16 is reflected by mirrors 17a, 17b, 1
The photoelectric conversion element 19 is guided by the lens 17d and guided by the lens 17d.
Imaged on top. The electric signal output from the photoelectric conversion element 19 is A / D converted by an A / D converter 21 to be converted into 8-bit digital image data, and thereafter, the black signal generation circuit 22 converts luminance information into density information. Log conversion is performed to obtain image density data.

Here, as shown in FIG. 1 or FIG. 3, the image density data is corrected for each pixel in the main scanning direction by the main scanning unevenness correction circuit 50 of the present invention. The correction method in the main scanning unevenness correction circuit will be described later in detail.

The 8-bit digital image data signal generated as described above is transmitted to the LED driving circuit 2 which is a feature of the present invention.
4c (see FIG. 18) and the LED drive circuit 24c
Is a well-known PWM circuit, and sets the LED as the light emitting element 20c to o according to the magnitude of the input image density signal.
The light emission time to be n / off is modulated. Light emitting element 20c
Are arranged in the main scanning direction.

The LED light driven and emitted according to the image signal as described above is written on the photosensitive drum 1 to form a digital electrostatic latent image as image information.

In this embodiment, an amorphous silicon drum is used as the photosensitive drum 1. Amorphous silicon drums are characterized by high stability of the characteristics of the conductive substrate, high durability and long life.

The respective steps for explaining the image forming process of the present embodiment are the same as those of the first embodiment.

An image deletion prevention sequence based on detection of a high humidity environment, which is a feature of the present embodiment, will be described below. The following summarizes each condition of the sequence for each purpose.

Here, the operation of Example 1 of the present embodiment will be described step by step with reference to FIG.

When the environment is defined as a specific moisture content region, the moisture content W ≧ 9
When it is detected as g, it is determined that the environment is a high humidity environment (a). The 200th copy is assumed to be a copy start when the default number of copies (specified number of intervals) of the total number of copies and prints is 200. It detects that the specified number of sheets has been reached, and operates to perform the post-rotation black band during post-rotation at the end of this job. After the laser exposure of the image area is completed, the drum drive motor is operated to keep the drum idling, and at the same time, the developer drive motor is operated to rotate the sleeve of the developer, and at the same time, the cleaner drive motor (main motor) is operated. Then, the cleaner system also idles. Further, the polygon mirror rotation drive of the laser scanning system continues its operation.

The primary charging is also continuously performed, and the output is performed using the same control value as that of the image area, that is, the potential control value at the closest time as the charge amount. If there is no previous data, output is performed with the program default value. The output extension time is equal to or longer than the black band width, and has a slightly extra charged area before and after the black band. In total, this is a time corresponding to 20 mm or more in the circumferential direction on the drum. The length in the main scanning direction is equal to or greater than the nominal width of A3 width in the image area center distribution.

Next, in the laser exposure, the image area is completed, the light is turned off once for a specific time, and then the lighting for the black band is performed. The laser is turned on with the same power control value as in the image area.
If there is no such data, output is performed with the program default value. FF for image area as image data level
hex solid. The length in the main scanning direction is a nominal width of A3 width in image area center distribution. In other words, laser beam scanning is performed with a width that does not include the adjustment tolerance for registration in the main scanning direction (lateral registration). Here, the 297 mm image area FFhe
x output is performed. The output time is a time corresponding to the black band width, and here is a time corresponding to 20 mm in the circumferential direction on the drum. Also, before outputting the FFhex, a bias current is applied to make the laser output slightly rise in order to speed up the rise of the laser output. The output data is not limited to FFhex, but may be 80hex or 40hex depending on the state of the image forming apparatus.
x may be used.

Next, in development, an AC voltage + DC voltage is output. The AC voltage is output at a standard voltage, and the DC voltage is output at a DC control value similar to the image area. In the present embodiment, the black band width is its DC control value of 280 V. However, a DC control value of 300 V for the non-image area is output so as to completely cover the area where the primary charging before and after the black band width is output. The setting is such that reversal development in the area of only primary charging is minimized. FIG. 21 shows only the DC voltage, but the AC voltage is
On in the area that further covers the slope of the voltage (for non-image)
are doing. If there is no previous data, a DC control value is output with a program default value. The output time is equivalent to the black band width, and here, 20 times in the circumferential direction on the drum.
It is a time equivalent to mm. The DC value is set so that it can be input on the scanning panel and the black band density can be changed.

After the toner band has been formed on the drum, the black toner band is carried to the drum cleaning device and is stopped by the edge of the cleaning blade, where the accumulated toner removes the layered material on the drum surface. Since this scraping effect is proportional to the rubbing time, the time should be as long as possible to secure as long as possible.

Further, in the above black band formation, the black band data of the post-rotation black band is controlled (the black band width is fixed) according to the detected moisture content as shown in FIG. By fixing the black belt image data, it is possible to supply the black belt toner to the most appropriate cleaning blade according to the environmental humidity, and the effect of the moisture absorbing substance on the drum affecting the image according to the environmental moisture content Since it is possible to supply the toner according to the degree, it is possible to avoid wasteful toner consumption due to excessive toner black band in a relatively low moisture content even in a high humidity environment. Conversely, when the water content is extremely high, by supplying more toner, it is possible to control so as to sufficiently remove the moisture absorbing portion of the surface layer of the attached moisture absorbing substance. The selection of the control content is variable depending on the usage status of the image forming apparatus. In particular, it is desirable that the larger the number of sheets used during the specific period is, the larger the black band width is, and the selection is made so as to remove a large amount of the hygroscopic substance adhered. As a result, it is possible to appropriately cope with any environmental humidity range, and to always provide a good image.

As described above, the most severe humid environment (water content per unit volume of cubic meter is 9
g / m ³ or more), the image forming apparatus can obtain a good image over a long period regardless of the environment.

Hereinafter, a method of correcting unevenness in the main scanning direction when density unevenness occurs in the developing device and other portions will be described in detail.

A description will be given using the flow of operation for creating the correction table 50 in FIG. 12 as in the first embodiment.

(1) The image forming apparatus of the present embodiment has an “improving image mode” as an image unevenness improvement mode in the input interface, and the mode is first started.

(2) Next, an axial direction unevenness (main scanning direction unevenness) correction mode is selected.

(3) Press the key to start the axial unevenness correction mode, and start.

(4) The image forming apparatus outputs a test image sample as shown in FIG. As the conditions for forming this sample, in order to form an image such as a completely solid black, a halftone halftone, and a solid white, three types of image exposure conditions obtained by the above-described primary charging conditions for forming the surface potential (see FIG. 11, F0, 80, and 00 hex), developed, transferred, and fixed under the above-described developing conditions to output a sample.

(5) The output sample is placed on the platen by the mode executor at a specific position at the front end and the front or back side of the sample in the paper passing direction. Determine whether it has been detected.

(6) When it is determined that the loading is completed, the original is read by the reader as described above. It is desirable that the reading by the reader be performed at a resolution of about 400 to 600 dpi.

(7) Whether this original is a test image sample or not is determined based on whether or not the density gradation is the same pattern.

(8) If it is determined that the sample is a test image sample, the distribution of the density in the axial direction is calculated as shown in FIG. When a test image sample is formed at F0, 80, and 00 hex of the PWM level, the read density distribution of the halftone portion of 80 hex at which unevenness is most easily detected is calculated (the density distribution is calculated at F0, 80, and 00 hex, respectively). May be done.)

(9) Referring to FIG.
In the case of 5, the increase / decrease of the read density distribution of the halftone portion with respect to 0.5 is calculated so as to correspond to each pixel in the main scanning direction. If the minus correction is represented by a negative sign and the plus correction is represented by a plus sign, the required correction density becomes a required correction density as shown in FIG.

(10) The correction light amount (correction level) for each pixel of the dot exposure laser is obtained from FIG. As an example, in FIG. 14, the required correction density is +0.8.
In the case of, the surface potential is -200V and the drum surface light amount is + 200V.
This indicates that a correction of +80 hex is required for image data of 0.25 μJ. A correction amount level corresponding to each pixel in the main scanning direction is assigned by this capacity, and a correction table is created. Here, this mode ends, and the operation panel, which is the input interface unit of the image forming apparatus, returns to the normal copy or print mode.

As described above, the main switch on
When the temperature of the fixing thermistor at the time is below a specific temperature and the environment is in a specific moisture content region (below), it is determined that the environment is one morning and a high humidity environment (and each environment), and the drum idle rotation according to the moisture content region ( The developing unit and the cleaner system also idle), and at the same time as the start of idle rotation, primary charging, laser exposure, and development are performed on the drum to form a black toner band. By correcting the density unevenness at the writing level, the density is sufficient, and the developability is improved until the reproducibility of isolated dots can be sufficiently ensured, and the first copy image in the morning in a high humidity environment In this case, it is possible to obtain a high-quality image with high density and no density unevenness in the longitudinal direction (main scanning direction) by using a small-sized image forming apparatus.

In the first to third embodiments, an example has been described in which an image is formed by a binarization process using an error diffusion method or the like (or a dither method or the like). However, an image is formed according to a PWM method. Of course, it can be applied to the case. Further, when an image is formed by the PWM method, basically, pixels having different shades (actually, pixels having different sizes due to area modulation and having different shades when viewed from human eyes) are formed. Perceived.)
If the density distribution is simply read by the reader unit of the embodiment, the density unevenness of each pixel can be corrected. However,
In order to read without shifting even one pixel, it is necessary to read at a very high precision. As a practical problem, it is difficult to determine the characteristics of each pixel formed on the printer engine side from the read image. Printer resolution is 600d
In the case of pi, it is necessary to read an image with a deviation of less than 1/600 inch, which is very difficult as a practical problem. Therefore, as described above, PW
Even in the case of forming by the M method, it is desirable to detect the density unevenness in the main scanning direction based on the average value of a plurality of pixels consecutively read in the main scanning direction, and to correct it.

Although the present invention has been described by taking a printer as an example, the present invention can also be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.).

In this case, since the above processing can be performed in a portion corresponding to the host computer, the present invention uses a storage medium storing the program code of software for realizing the functions of the above-described embodiment, as a system or a system. This can also be achieved by supplying the program code stored in a storage medium to a computer (or CPU or MPU) of the system or the apparatus for reading and executing the program code.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
CD-R, magnetic tape, nonvolatile memory card, RO
M or the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiments are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. It is needless to say that the present invention includes a case where the system performs some or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, The CPU provided in the function expansion board or function expansion unit performs part or all of the actual processing,
It goes without saying that the processing may realize the functions of the above-described embodiments.

[0165]

As described above, according to the present invention,
Even when an image forming apparatus having an a-Si photoconductor (image carrier) of a laser scanning exposure system is used in a high humidity environment, ozone generated by corona discharge, a discharge product, and rubber of a paper feed roller and a transport roller. Even if a substance deposited from the material adheres to the surface of the photoreceptor, it is possible to prevent the occurrence of image deletion. According to this, in order to adhere the developer to the photoreceptor in a specific number of sheets and supply it to the cleaning unit, the polishing is performed before the flowing material is firmly laminated on the photoreceptor surface, so that the photoreceptor surface is It is possible to enhance the polishing effect, and it is possible to prevent the occurrence of streak images in the image flow state even during the long-term use of the image forming apparatus that forms digital data with minute dots or the initial image after power is turned on,
Deterioration of image deletion can be prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment.

FIGS. 2A to 2C are diagrams schematically showing a relationship between a surface potential of a photosensitive drum and a developing bias.

FIG. 3 is a block diagram illustrating image processing according to the first embodiment.

FIGS. 4A to 4C are diagrams showing a relationship among image data for each pixel, a drive signal of a laser, and a drive current.

FIGS. 5A and 5B are diagrams illustrating laser lighting of binary image data.

FIG. 6 is a diagram showing general IL characteristics (drive current-light amount characteristics) of a laser.

FIGS. 7A to 7C are schematic diagrams in which the cause of the occurrence of density unevenness in the main scanning direction is analyzed.

FIG. 8 is a diagram showing a relationship between a charging wire current and a drum surface potential.

FIG. 9 is a diagram illustrating a relationship between an image exposure amount and a drum surface potential.

FIG. 10 is a diagram illustrating a relationship between a development contrast potential and a development density.

FIG. 11 is a diagram illustrating a relationship between image data and a wide-area integrated image exposure amount.

FIG. 12 is a flowchart illustrating an outline of a flow of a correction operation.

FIGS. 13A to 13C are diagrams showing test image samples, read densities, and densities required for correction.

FIG. 14 is a diagram illustrating a correction amount.

FIG. 15 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a second embodiment.

16A to 16F are schematic diagrams for explaining an image forming process in a two-color image forming mode according to the second embodiment.

FIG. 17 is a block diagram illustrating image processing according to the second embodiment.

FIG. 18 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to a third embodiment.

FIG. 19 is a longitudinal sectional view showing a schematic configuration of a conventional image forming apparatus.

FIG. 20 is a diagram showing a specific circuit configuration of a main scanning unevenness correction circuit.

FIG. 21 is a diagram showing a sequence in the first embodiment.

FIG. 22 is a diagram showing black band width and water content control of black band writing data.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum) 2 Primary charger (scorotron charger) 3 Exposure means (exposure apparatus) 7 Developing apparatus 8 Transfer apparatus (transfer charger) 20, 20a, 20b Exposure means (laser) 20c Exposure means (light emission) Element, LED) 50 Correction value creation means (main scanning unevenness correction circuit) 62 Developer charge control charger (post-charger)

Claims (15)

[Claims] A charging means for uniformly charging the surface of the image carrier; an exposure means for exposing the charged surface of the image carrier in accordance with image data to form an electrostatic latent image; Developing means for attaching toner to the image and developing it as a toner image;
Transfer means for transferring the toner image formed on the image carrier to a transfer material, fixing means for fixing the toner image on the transfer material, and cleaning means for cleaning the surface of the image carrier after transfer of the toner image An image forming apparatus comprising: a moisture detecting unit configured to detect a moisture amount of a surrounding environment; and a control unit configured to control an image forming operation. Immediately after the image area after the specified number of image formations has been counted when it is detected that the water content is equal to or more than the specific moisture amount, the image carrier is operated by operating the charging unit, the exposure unit, and the cleaning unit. An image forming apparatus, which forms a toner image on a body. 2. The image forming apparatus according to claim 1, further comprising means for converting the multi-valued image data into binary data. 3. An intermediate density between the black image data level and the white image data level detected density based on the tone density reproduction characteristic in the image forming unit detected by the density characteristic detecting means, and the calculated value is calculated. 3. The image forming apparatus according to claim 1, further comprising a correction value creating unit configured to perform correction on the image data by setting the target density as a target density. 4. The controller according to claim 1, wherein the width of the toner black band, which is a toner image formed on the image carrier, and image writing data for forming a black belt are determined according to the amount of moisture detected by the moisture detector. The image forming apparatus according to claim 1, wherein the image forming apparatus performs control. 5. The image forming apparatus according to claim 4, wherein said moisture detecting means detects a moisture content in the air. 6. The image forming apparatus according to claim 5, wherein the specific moisture amount is 9 g / m ³ or more. 7. The image forming apparatus according to claim 1, wherein the charging unit performs charging immediately after an image forming area has been counted a specified number of times with a charging output value equivalent to that used in the previous image forming. 7. The image forming apparatus according to claim 1, wherein charging is performed for a length corresponding to a circumferential length of the toner image formed on the body. 8. The image forming apparatus according to claim 6, wherein the exposure unit is configured to expose the toner image formed on the image carrier to a length corresponding to an axial length of the toner image immediately after the image forming area is counted a specified number of times. The axial length of the toner image is shorter than the maximum exposure length at both longitudinal ends, and is equal to or greater than the standard image forming area. Or the image forming apparatus according to 7. 9. The image bearing member according to claim 1, wherein the image bearing member is a photosensitive drum in which a photoconductor for forming an electrostatic latent image is formed on a cylindrical conductive substrate in a thin layer. , 5, 6, 7,
Or the image forming apparatus according to 8. 10. The image forming apparatus according to claim 9, wherein the photosensitive drum uses an a-Si photosensitive member. 11. The exposure means is a minute spot exposure means, and forms a latent electrostatic image on the surface of the image carrier by scanning and exposing a laser beam capable of digital exposure for each pixel. The image forming apparatus according to claim 9, wherein: 12. The image forming apparatus according to claim 1, wherein the exposure unit performs black image data level exposure at a laser lighting output value equivalent to that used in the previous image formation immediately after the image formation area after the specified number of image formations has been counted. The image forming apparatus according to claim 9, wherein the exposure is performed at the same time as the length corresponding to the circumferential length of the toner image formed on the image carrier. 13. The image forming apparatus according to claim 1, wherein the exposure unit drives a plurality of light emitting elements arranged in the main scanning direction to perform exposure, thereby forming an electrostatic latent image on the surface of the image carrier. Item 11. The image forming apparatus according to Item 9 or 10. 14. The method according to claim 1, wherein said developing means uses a one-component developer.
The image forming apparatus according to 8, 9, 10, 11, 12, or 13. 15. The image forming apparatus according to claim 1, wherein the developing unit develops immediately after an image forming area after a specified number of image forming operations is performed, with a developing bias output value equivalent to that used in the previous image forming. The image forming apparatus according to claim 1, wherein development is performed to a length corresponding to a circumferential length of the toner image formed on the carrier.
The image forming apparatus according to 8, 9, 10, 11, 12, 13, or 14.